Heating fuel oil



Patented Jan. 4, 1944 UNITED STATES PATENT OFFICE Richard G. Clarksonors to E. I. du Pont Wilmington, Del., 2. c

, Wilmington, Del., assignde Ncmours & Company,

orporation of Delaware No Drawing. Application June 21, 1941, Serial No.399,238

11 Claims. (CI. 44-08) This invention relates to heating fuel oils, thatis, fuel oils employed in oil burners and the like for heating purposesand particularly to heating fuel oils which have been treated to improvetheir combustion properties and to decrease their tendency to form sootand residual carbonaceous deposits.

It has been proposed to incorporate various materials into heating oilsfor removing soot and improving combustion characteristics. Amongst thecompounds, so proposed, are copper, lead, calcium, zinc, iron, cobaltand manganese naphthenates. effect for their purpose, it is desirable tohave more effective compounds. Also, compounds, generally employed forthis purpose, are also very active to accelerate deterioration of thefuel oil in storage, whereby large amounts of sludge are formed and theusefulness of the oil is greatly impaired and sometimes destroyed.

It is an object of our invention to provide heating fuel oils ofimproved combustion properties. Another object is to treat heating fueloils with compounds which are more effective for improving thecombustion characteristics of the oils. A further object is to treatheating oils to greatly improve their combustion characteristics withoutgreatly increasing their tendency to form gummy deposits in storage. Astill further object is to provide heating oils of better While suchcompounds have some combustion characteristics and stability in storagethan those heretofore known. Other objects are to provide newcompositions of matter and to advance the art. Still other objects willappear hereinafter.

The above and other objects may be accomplished in accordance with ourinvention which comprises incorporating, in a heating fuel oil, anoil-soluble compound of chromium in such proportion that there ispresent from about 1 to about 100 parts of chromium in about one millionparts of oil. We have found that, by so treating the oil, its combustioncharacteristics are greatly improved and its tendency toward theformation of gummy deposits is not greatly accelerated. We have foundthat the compounds of chromium are much more effective thancorresponding compounds of other metals which have been proposed forthis purpose and improve the combustion characteristics of the oil to amuch greater extent. Furthermore, we have found that the compounds ofchromium are very much less active to catalyze deterioration and gumformation in the oil during storage than corresponding compounds ofother metals which have been employed for improving the combustioncharacteristics of heating oils. Accordingly, the heating oils of ourinvention, not only have better combustion characteristics thanpreviously known heating oils, but also are much more stable towarddeterioration and gum formation than previously known heating oils whichhave been treated with metal compounds to improve their combustioncharacteristics.

We have found that the effect of the compounds on the oil is a functionof the proportion of metal in the oil and does not depend upon thestructure of the compound added. Accordingly, it is only necessary thatthe chromium compound be soluble to such an extent that a sufiicientamount of the metal can be incorporated in the oil. Therefore, when werefer to an oil-soluble compound of chromium, we mean a compound whichis soluble to such an extent that it can be dissolved in the on in suchan amount as to provide from about 1 to about 100 parts of chromium inabout one million parts of the oil. With most oil-soluble compounds ofchromium, this will require the solution of from about 0.001% to about0.1% of the compound based on the oil. For example, the chromium soaps,such as the oleates, naphthenates and the like, and the chromiumdithiocarbamates will generally be employed in the proportion of about0.001% to about 0.1% based on the oil. Lesser amounts may be employed,but with less satisfactory results, while larger amounts would tend toresult in the production of objectionably large deposits of metal ashwithout appreciably improving the results.

Since the effect produced is a function of the metal, chromium, ratherthan of the structure of the compound in which it is combined, alloil-soluble compounds of chromium may be employed in accordance with ourinvention. However, we generally prefer to employ the chromium soaps orthe chromium salts of dithiocarbamic acids, because of their desirableproperties as well as their cost. The chromium salts of the dialkyldithiocarbamic acids will be pre ferred over the chromium salts of otherdithiocarbamic acids. Suitable chromium soaps are chromium oleate,chromium linoleate, chromium stearate and the chromium naphthenates. Ofthe chromium soaps, we preferto employ the chromium naphthenates andparticularly the basic chromium naphthenates.

It has been found that the basic chromium salts of naphthenic acids, inwhich the ratio of naphthenic acid is from about 1.9 to about 2.7

molecular proportions for each atomic proportion of chromium and inwhich the chromium dinaphthenates predominate, when dissolved in theoil, produce solutions of unusually low viscosity, that is, ofmaterially lower viscosity than can be obtained with chromiumnaphthenates in which the proportions of naphthenic: acid are different.The most desirable chromium naphthenates in this respect are thosewherein the ratio of naphthenic acids to chromium is within the range offrom 2.0 to 2.5 molecular proportions for each atomic proportion ofchromium. Chromium naphthenates, containing 2.07, 2.15, 2.28, 2.46, and2.47 molecular proportions of naphthenic acids, respectively, to oneatomic proportion of chromium, have been employed very satisfactorily.The chromium naphthenates may be prepared from a single pure naphthenicacid, but will generally be prepared from a mixture of naphthenic acidsobtained from petroleum, whereby the naphthenates are obtained asmixtures of chromium salts of such mixtures of naphthenic acids. 1

The basic chromium naphthenates can be made by various methods; e. g.,methods which have heretofore been employed for preparing basic aluminumsoaps, such as basic aluminum oleate and basic aluminum naphthenate. Onemethod, which can be readily adapted to produce basic chromiumnaphthenates, is that disclosed by Faragher et al. in Patent 1,550,608,employing chromium hydroxide for the purpose.

The oils, in which the oil-soluble chromium compounds are to beemployed, are the usual heating fuel oils employed in oil burners fordomestic and commercial heating purposes at substantially atmosphericpressures. The oils will generally be petroleum oils and will range fromkerosene and very light fuel oils of 40 A. P. I. gravity and higher toheavy residual fuel oils of 10 A. P. I. gravity or less. The heatingfuel oils of our invention should be free of suspended solid matter toobtain satisfactory operation and use.

In order to illustrate our invention more clearly, the preferredembodiments thereof and the advantageous results to be obtained thereby,the following examples are given in which the test apparatus comprise adomestic oil burner provided with a spray-type injection nozzle, ratedat 1.2 gallons per hour at 100 pounds per square inch, and positive airfeed. In order to provide a steady and reproducible feed of the fuel,the oil pump was disconnected from the system and pressure applied tothe fuel tank by means of compressed nitrogen, using an accuratereducing valve. The combustion chamber was a 55-gallon black iron drumfitted with a tight cover carrying a 6-foot stack, 6 inches in diameter.The drum was fitted with a hole of a size just sufficient to admit thewindpipe of the burner so that the entire air supply to the combustionchamber was through the windpipe, The combustion air was forced throughthe windpipe by constant speed fan, the air supply being regulated by acircular cover plate on the orifice of the inlet to the fan. The coverplate could be moved in a direction perpendicular to the plane of theorifice while maintaining it in a plane parallel to the plane of theorifice and definitely fixed in any desired position by means of setscrews. The term orifice opening, as employed in the examples, means thedistance between the cover plate and the orifice.

Emu I An unblended light fuel oil of 45 A. P. I. gravity was burned inthe test apparatus, using a nitrogen pressure of 125 pounds per squareinch on the fuel tank. The air inlet opening was nearly closed, causingdense smoke to rise from the stack, and then very slowly opened to thepoint at which the smoke just disappeared. The orifice opening was thenmeasured and found to be 0.60 cm. Stack gas analysis showed 10.0% CO2,corresponding to 44% excess air.

The above experiment was then repeated, using the same base oil to whichhad been added 0.1% of its weight of chromium tri-naphthenate, preparedfrom a mixture of naphthenic acids having an acid number of 260. Theorifice opening, at which smoke disappeared, was 0.28 cm. The stack gascontained 12.1% CO2, corresponding to 25% excess air. The reduction, inair inlet opening, amounted to 53% and, in excess air, to 43%.

' Erfiulru lI Samples of the light fuel oil of Example I were blendedwith 0.10% by weight of each of eight metallic dibutyl dithiocarbamates.These samples of blended fuel oil were burned in the test apparatus asdescribed in Example I. The metallic dibutyl dithiocarbamates werechosen for test since, in the concentrations used, they do not affectthe viscosity, and consequently the.

the following Table I:

Table I Weight Wei ht Minimum Metallic dbutytl dithiocarpercent 0!pemgnt air inlet ama e 9 8, additive of metal percent The results, givenin the table, show that chromium was the most effective metal indecreasing the permissible air inlet opening, thus permitting smokelesscombustion with the least amount of excess air, despite the fact that itwas lowest in actual weight of metal added of the entire series.

It would normally be expected that a metal compound, which was an activecatalyst for the oxidation of soot and carbonaceous residues, would alsobe extremely active in promoting oxidation of organic compounds at lowertemperatures. For example, the naphthenates of cobalt, manganese andlead are widely used as driers" or oxidation catalysts in paints. Thedetrimental effects of copper, as an oxidation catalyst in rubber andgasoline in storage at ordinary temperatures, are also well recognized.Many examples of the effects of iron in this respect are known.

It has been found, surprisingly enough, that oil-soluble chromiumcompounds, while very efficient catalysts for the products of incompletecombustion, have little effect in accelerating the formation of gum infuel oil in storage, in comparison with other agents which have beenrecommended for reducing combustion residues. In D. S. Patent 2,141,848,Adams recommends the use of the naphthenates of calcium, copper, lead orzinc in fuel oil as soot removing compounds. Fischer et al. in U. S.Patent 2,230,642, discloses fuel oils of improved combustion propertiescontaining the naphthenates of cobalt, iron or manganese as additionagents.

The effect of these naphthenates, upon gum formation in fuel oil, wascompared with that of chromium naphthenate. An accelerated aging testwas used in which the blended fuel oil was heated in an open beaker at100 C. for 24 hours. The gum content of each sample was then determinedby evaporating the oil in a tared beaker in a stream of heated air. Theapparatus and procedure was that of A. S. T. M. method D381-36 for gumin gasoline, with the exception that the temperature of the bath wasraised to 185 C. A description of such tests and the results thereofappears in the following Example III.

EXAMPLE III A light fuel oil of 35 A. P. I. gravity was aged by the testprocedure indicated above and the gum content, after the aging,wasdetermined by the outlined modification of A. S. T. M. methodD381-36. In an identical manner the gum, after a was determined forsamples of the same base oil blended with 0.05% by weight of eightmetallic naphthenates. The gum values for these samples were correctedby subtracting from each, except the unblended sample, 42.5 mg./ 100cc., the weight of metallic naphthenate originally added. The results ofthese tests are shown in Table II, in which is also given the amount ofgum which may be charged to acceleration of oxidation by the combustioncatalyst. Each figure is an average of three parallel determinations.

It will be noted that chromium naphthenate accelerates gum formation toa lesser extent than any of the prior art combustion catalysts and that,in particular, it is far less deleterious than cobalt, copper, iron,lead and manganese which were shown, in Example II, to approach it mostclosely in effectiveness for our purposes.

Practical tests of fuel oils, containing chromium naphthenates, havebeen carried out in domestic oil burner installations. It has been shownthat furnaces, which contained deposits of soot and carbonaceousresidues due to faulty adjustment of the system or poor draft, can becleaned by burning of the same 011, which caused such deposits, to whichhas been added as little as 0.02% of chromium naphthenate. The use ofsuch blended oil for one or two days, in many cases, has restored suchfurnaces to a good state of cleanliness without adjustment of the draftor oil pressure or other changes in the system.

It will be understood that the preceding examples have been given forillustrative purposes only and our invention is not to be limited to thespecific embodiments disclosed therein, but we intend to claim ourinvention broadly as in the appended claims. It will be readily apparentto those skilled in the art that many variations and modifications maybe made within the scope of our invention without departing from thespirit thereof. For example, other oil-soluble compounds of chromium,such as chromium beta diketonate compounds, represented by chromiumacetyl acetonate and chromium propionyl acetonate, chromium laurylphthalate, chromium oleyl phthalate, chromium phenyl stearate, chromiumphenyl chloro-stearate, chromium p-amyl phenoxy acetate and chromiumresinates, may be substituted for the compounds given in the examples.

It will be apparent, from the above description of our invention, thatwe have provided heating fuel oils of greatly improved properties. Ourheating fuel oils may be used under conditions of air supply which, inthe case of unblended fuels, lead to the formation of soot and residueson heating surfaces, thereby causing losses in thermal efliciency. This,particularly in domestic heating installations, means that theadjustments of the burner need not be so carefully controlled asheretofore and assures trouble-free operation with a minimum ofattention by the owner. In commercial installations, a number of furtheradvantages are obtained. Due to the fact that a lower percentage ofexcess air can be used without leading to objectionable smoke and soot,the stack losses can be materially decreased, thereby improving thermalefiiciency. Furthermore, the

complete combustion of all soot and residues produces a greater thermaloutput per gallon of fuel and the greater cleanliness of the boilertubes and other exchange surfaces improves the heat transfer.Furthermore, since the heating fuel oils of our invention are morestable toward the formation of gummy deposits, there is less danger ofthe feed lines and pumps becoming clogged and cleaning of the storagetanks, feed lines and pumps is only necessary at less frequentintervals, thereby resulting in further large economies to the consumer.

We claim:

1. A liquid heating fuel oil composition, having improved combustioncharacteristics, which comprises a liquid heating fuel oil,substantially free of solid particles, and containing an oil-solublecompound of chromium in such proportion that there is present from about1 to about parts of chromium in about one million parts of oil and in aproportion sufiicient to materially improve the combustioncharacteristics of the oil.

2. A liquid heating fuel oil composition, having improved combustioncharacteristics, which comprises a liquid heating fuel oil,substantially free of solid particles, and containing an oil-solublechromium soap in such proportion that there is present from about 1 toabout 100 parts of chromium in about one million parts of oil and in aproportion sufficient to materially im-- prove the combustioncharacteristics of the oil.

3. A liquid heating fuel oil composition, having improved combustioncharacteristics, which comprises a liquid heating fuel oil,substantially free of solid particles, and containing oil-solublechromium naphthenates in such proportion that there is present fromabout 1 to about 100 parts of chromium in about one million parts of oiland in a proportion suflicient to materially improve the combustioncharacteristics of the oil.

4. A liquid heating fuel oil composition, having improved combustioncharacteristics, which comprises a liquid heating fuel oil,substantially free of solid particles, and containing oil-soluble basicchromium naphthenates in such proportion that there is present fromabout 1 to about 100.parts of chromium in about one million parts of oiland in a proportion suflicient to materially improve the combustioncharacteristics of the oil.

5. A liquid heating fuel oil composition, having improved combustioncharacteristics, which comprises a liquid heating fuel oil,substantially free of solid particles, and containing oil-soluble basicchromium salts of naphthenic acids in which the ratio of naphthenicacids is from about 1.9 to about 2.7 molecular proportions for eachatomic proportion of chromium and in which chromium di-naphthenatespredominate, the chromium salts being in such proportion that there ispresent from about 1 to about 100 parts of chromium in about one millionparts of oil and in a proportion suificient to materially improv thecombustion characteristics of the oiL 6. A liquid heating fuel oilcomposition, having improved combustion characteristics, which comprisesa liquid heating fuel oil, substantially free of solid particles, andcontaining a mixture of oil-soluble chromium salts of a mixture ofnaphthenic acids in which the ratio of naphthenic acids is from 2.0 to2.5 molecular proportions for each atomic proportion of chromium and inwhich chromium di-naphthenates predominate, the chromium salts being insuch proportion that there is present from about 1 to about 100 parts ofchromium in about one million parts of oil and in a proportionsufficient to materially im prove the combustion characteristic of theoil.

7. A liquid heating fuel oil composition, having improved combustioncharacteristics, which comprises a liquid heating fuel oil,substantially free of solid particles, and containing a mixture ofoil-soluble chromium salts of a mixture of naphthenic acids in which theratio of naphthenlc acids is about 2.47 molecular proportions for eachatomic proportion of chromium and in which chromium di-naphthenatespredominate, the 6 chromium salts being in such proportion that there ispresent from about 1 to about 100 parts of chromium in about one millionparts of oil and in a proportion sufficient to materially improve thecombustion characteristics of the oil.

8. A liquid heating fuel oil composition having improved combustioncharacteristics, which comprises a liquid heating fuel oil,substantially free of solid particles, and containing oil-sclublcchromium di-naphthenates in such proportion that there is present fromabout 1 to about 100 parts of chromium in about one million parts of oiland in a proportion suillcient to materially im prove the combustioncharacteristics of the oil.

9. A liquid heating fuel oil composition, having improved combustioncharacteristics, which comprises a liquid heating fuel oil,substantially free of solid particles, and containing an oil-solublechromium salt of a dithlocarbamic acid in such proportion that there ispresent from about 1 to about 100 parts of chromium in about one millionparts of oil and in a proportion sufilcient to materially improve thecombustion characteristics of the oil.

10. A liquid heating fuel oil composition, having improved combustioncharacteristics, which comprises a liquid heating fuel oil,substantially free of solid particles, and containing an oil-solublechromium salt of a dialkyl dithiocarbamic acid in such proportion thatthere is present from about 1 to 100 parts of chromium in about onemillion parts of oil and in a proportion suflicient .to materiallyimprove the combustion characteristics of the oil.

11. A liquid heating fuel oil composition, having improved combustioncharacteristics, which comprises a liquid heating fuel oil,substantially free of solid particles, and containing chromium dibutyldithiocarbamate in such proportion that there is present from about 1 toabout 100 parts of chromium in about one million parts of oil and in aproportion suflicient to materially improve the combustioncharacteristics of the oil.

FREDERICK B. DOWNING.

CERTIFICATE OF CORRECTI ON Patent No. 2,558,578. January h, 19 414..

FREDERICK B. DOWNING, ET AL.

It is hereby certified that error appears in the printed Specificationof the above numbered patent requiring correction as follows: Page 2,sec- 0nd column, line 52, in the table, third column thereof, for"0.0083' read -0.008h-- and that the said Letters Patent should be readwith this correcti on therein that the same may conform to the record ofthe case in the Patent Office Signed and sealed this Lynn day of April,A. D. 19%.

Leslie Frazer (Seal) Acting Commissioner of Patents.

